Effect of Hygrothermal Aging on Repeated Low‐Velocity Impact Resistance and Damage Accumulation of Glass Fiber‐Reinforced Polymer Composites

The effects of hygrothermal aging on the impact mechanical response and the damage accumulation of composites under repeated low‐velocity impacts were investigated in this study. Laminates were aged in tap water and artificial seawater aging environments at 60°C for 1200 h. Repeated impacts were then carried out until the appearance of perforation failure at 20 J. Combining macroscopic and microscopic damage morphology, the dynamic mechanical response curves of both unaged and aged laminates were analyzed. The variations of mechanical characteristics, such as the peak force, maximum deformation and dissipated energy were discussed as the impact number increased. The degree of damage accumulation was also evaluated for the impacted laminates. Results showed that hygrothermal aging promoted the occurrence of matrix cracking and the development of delamination. Fiber breakage occurred earlier in aged laminates with fewer impact numbers. Compared to unaged laminates, aged laminates showed lower peak force, larger deformation and higher absorbed energy. Total absorbed energy decreased by 16% for tap water aged laminates and by 32% for seawater aged laminates. Moreover, aged laminates exhibited a larger damage area and faster damage accumulation under the same impact number. Overall, hygrothermal aging significantly reduced the repeated low‐velocity impact resistance and damage tolerance of composite laminates.